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Biomedical subjects

H Wright

Publications and source records attributed to H Wright.

At least 37 records · Page 2Linked to original sources
PubMed2000

Single-dose oral toxicity study of a cross-linked sodium polyacrylate/polyvinyl alcohol copolymer in chickens (Gallus domesticus).

A single-dose oral toxicity study of a grafted copolymer of cross-linked sodium polyacrylate with polyvinyl alcohol was conducted in chickens (Gallus domesticus) to demonstrate this copolymer's safety for use as a hydration medium in recently hatched poultry chicks. Three experimental groups, each composed of 25 male and 25 female 1-day-old chicks, were administered a one-time dose of 0, 3, or 6 g of the hydrated test article by gavage. All chicks were monitored daily for mortality and morbidity during their typical grow-out period of approximately 8 weeks. Interim sacrifices of one animal of each sex from each treatment group were made at 1, 2, 4, and 6 weeks. All surviving animals were necropsied at the end of the study. A single dose of up to 6 g of hydrated copolymer did not adversely affect these animals during their grow-out period. Mortality was comparable across all experimental groups, as no statistically significant survival differences were found. Body weights were also comparable across the three experimental groups at all time points during the study, and no statistically significant differences were detected in mean terminal body weights among the groups. Finally, lesion frequencies were similar across the three experimental groups, with none of the lesions deemed related to administration of the test article. Thus, the safety of this cross-linked sodium polyacrylate/polyvinyl alcohol copolymer has been demonstrated for its intended use.

Acrylic Resins↗
PubMed2000

Effect of transjugular intrahepatic portosystemic shunt on thrombocytopenia associated with cirrhosis.

Thrombocytopenia is a frequent complication of cirrhosis. Its pathogenesis is not well known, but it has been suggested that splenic congestion induced by portal hypertension may be a major contributory factor. However, the available data regarding the effect of portal decompression either by surgical shunts or transjugular intrahepatic portosystemic shunt (TIPS) on peripheral platelet count in cirrhotics is conflicting. We studied the effects of TIPS on platelet count and mean platelet volume, following a successful TIPS placement. The platelet count had a tendency to decrease but was not statistically significant (120,100 +/- 72,100/mm3 before TIPS vs 99,800 +/- 51,400/mm3 after TIPS). The mean platelet volume remained essentially unchanged (9.8 +/- 1.5 fL before TIPS and 9.9 +/- 1.5 fL after TIPS). These results confirm that TIPS has an unpredictable effect on platelet count in cirrhotic patients with thrombocytopenia. The lack of a consistent increase in the peripheral mean platelet volume following TIPS placement suggests that TIPS is unable to significantly enhance the release of platelets sequestered in the splenic compartment in portal hypertension.

Adult↗
PubMed2000

Healing at skin graft donor sites dressed with chitosan.

Chitosan is a derivative of chitin, extracted from the exoskeleton of lobsters, crabs and shrimps. As a semi-permeable biological dressing, it maintains a sterile wound exudate beneath a dry scab, preventing dehydration and contamination of the wound to optimise conditions for healing. In this study, evaluation of healing at split skin graft donor sites, dressed half with chitosan and half with a conventional dressing, showed that chitosan facilitated rapid wound re-epithelialisation and the regeneration of nerves within a vascular dermis. In addition, digital colour separation analysis of donor site scars demonstrated an earlier return to normal skin colour at chitosan-treated areas.

Adolescent↗
PubMed2000

Growth induced by incremental static stretch in adult rabbit latissimus dorsi muscle.

Incrementally applied static stretch over 3 weeks resulted in a 72 % increase in the weight of the in situ latissimus dorsi muscle in rabbits. True growth rather than tissue oedema was confirmed by increases in the protein content (130 %), the cross-sectional area of the type I fibres (30 %) and the muscle length (i.e. number of sarcomeres in series increased 25 %). Despite an increase in the proportion of fibres staining positive for the enzyme succinate dehydrogenase (SDH), the myosin ATPase stain showed no appreciable fibre type transformation. While total power output in the stretched muscle was unchanged, its maximum mass specific power output, as determined by oscillatory work loops, was decreased by 50 %. The cross-sectional area that was occupied by connective tissue increased from 15 to 19 % in the stretched muscles, with a concomitant increase in passive energy dissipation. Some incrementally stretched muscles were then allowed an additional 3 weeks of maintained stretch to determine whether the adaptive changes would be preserved or reversed. Previous gains in muscle weight, length and area of type I fibres all remained. In contrast, the connective tissue content and the passive properties returned to control values during this period.

Animals↗
PubMed1999

Utilizing daily interferon (alpha 2b) and ribavirin combination therapy in chronic hepatitis C: a preliminary report.

UNLABELLED: The optimal dose, frequency and duration of interferon alpha 2b and ribavirin combination for the treatment of chronic hepatitis C is still not clear. Preliminary hepatitis C virus kinetic studies have suggested that daily interferon (IFN) is more advantageous than less frequent administration. This report documents the preliminary findings of an investigative protocol to evaluate the efficacy of long-term (12 month), daily IFN alpha 2b and ribavirin combination therapy for chronic hepatitis C patients, who have either relapsed (relapsers) or not responded (non-responders) to previous IFN therapy. METHODS: 25 non-cirrhotic HCV patients were enrolled in an attempt to treat protocol. Patients were administered 3 million units (MU) IFN alpha 2b subcutaneously (SQ) and ribavirin 1000-1200 mg PO on a daily basis. RESULTS: Four patients were removed from the protocol because of noncompliance. The remaining 21 patients (10 relapsers, 11 non-responders) were evaluated at the end of their 12th week of treatment. Twelve patients (57%) became HCV-RNA negative and nine patients (43%) remain positive at the end of this period. CONCLUSION: Although further studies on larger patient populations are necessary, our preliminary data suggests that daily IFN alpha 2b and ribavirin treatment is highly effective, especially among patients who have relapsed from previous IFN treatment.

Adult↗
PubMed1996

Circadian rhythms of early morning awakening insomniacs.

It has been suggested that two types of insomnia, sleep onset insomnia and early morning awakening insomnia, may be caused by delays and advances respectively of circadian rhythms. Evidence supports the circadian rhythm phase delay of sleep onset insomniacs. The present study investigated the phase timing of circadian rhythms of early morning awakening insomniacs compared with a group of age matched good sleepers. A 24-h bed rest laboratory session was used to evaluate the endogenous core body temperature and urinary melatonin rhythms. Objective and subjective sleepiness were also measured every 30 min across the session with 10 min multiple sleep latency tests and Stanford Sleepiness Scale. Maximum and minimum phases of each individual's rhythm were identified using two-component cosine curve fitting. Compared with the good sleepers, the insomniacs had significant phase advances of 2-4 h for the temperature and melatonin rhythms. However, the 0-4 h advances of the sleepiness rhythms were not significant. This latter unexpected result was explained on the basis of variability of sleepiness measures. It was suggested that early morning awakening insomnia arises from phase advanced circadian rhythms which evoke early arousal's from sleep.

Adult↗
PubMed1995

Analysis of the fine specificities of sheep major histocompatibility complex class II-specific monoclonal antibodies using mouse L-cell transfectants.

The fine specificities of two panels of monoclonal antibodies (mAbs) for sheep major histocompatibility complex (MHC) class II molecules were determined using five mouse L-cell transfectants, each expressing a defined sheep DQ or DR MHC class II A/B gene pair. Using the transfectants in an indirect fluorescence antibody assay, previous immunochemical characterization of the mAbs was confirmed for 16 of 23 mAbs tested. The MHC class II subtype specificity (DQ or DR) of each mAb was assigned without interference from the products of other expressed class II loci. This allowed the identification of both cross-locus specificities as well as defining fine specificities of mAbs previously only partially characterized by immunochemical techniques.

Amino Acid Sequence↗
PubMed1995

A long thin electrode is equivalent to a short thick electrode for defibrillation in the right ventricle.

We hypothesized that a long thin right ventricular (RV) electrode would have equivalent defibrillation threshold (DFT) performance to a short thick electrode with approximately the same surface area. This could lead to thinner transvenous lead systems, which would be easier to implant. A thin (5.1 French) lead was compared to a standard control (10.7 French). The thin lead had an 8-cm RV electrode length with a surface area of 4.26 cm2. The standard lead had a RV electrode length of 3.7 cm and a surface area of 4.12 cm2. A 140-mu French capacitor 65%/65% tilt biphasic defibrillation shock was delivered between the RV electrode and a 14-cm2 subcutaneous patch. DFTs were determined following 10 seconds of fibrillation in 11 dogs by a triple determination averaging technique. The thin lead had a lower resistance (77.1 +/- 27.4 omega vs 88.9 +/- 30.3 omega, P < 0.001) than did the thick lead. There was no significant difference in stored energy DFTs (9.9 +/- 2.5 vs 10.3 +/- 2.7, P = 0.098 2-sided, P = 0.049 1- sided). This was in spite of the fact that the long thin lead had a portion of its RV coil extending above the tricuspid valve and, thus, not contributing efficiently to the ventricular gradients in the small dog heart. We conclude that a long thin right ventricular electrode and a standard short thick electrode had equivalent defibrillation performance. This preliminary result should be confirmed in clinical studies as it could lead to significantly thinner transvenous lead systems.

Animals↗
PubMed1995

Woven wire patches are superior to solid disks for subcutaneous electrodes: implications for active can defibrillation.

The housing of the implantable cardioverter defibrillator (ICD) is being considered for a remote electrode to replace the conventional subcutaneous woven wire patch. It is not clear that the solid smooth and rigid metal surface of the ICD housing will provide the same performance as does the woven wire patch. We compared a solid titanium disk to a titanium woven wire patch for defibrillation performance in a canine model. The patch had a smaller outline area, a slightly smaller conductive perimeter, and slightly less of a small feature surface area than did the disk. The remote electrode (disk or patch) was inserted at the point of maximal apical cardiac impulse. A commercially available endocardial electrode was placed in the right ventricle (RV). Conventional biphasic shocks (140-microFrench capacitor and 65% tilt) were delivered between the RV and subcutaneous electrode. The patch had significantly lower resistances than did the disk (81.6 +/- 8.0 omega vs 90.0 +/- 11.6 omega P < 0.006). The patch also had significantly lower stored energy defibrillation thresholds than did the disk (8.0 +/- 2.6 J vs 9.3 +/- 3.3 J, P < 0.007). In spite of smaller values for every geometrical dimension, the woven wire patch out performed the solid disk for defibrillation with conventional biphasic waveforms. Since the ICD housing is typically smooth titanium, the use of waveforms better suited for the active can configuration may deserve a systematic evaluation.

Animals↗
PubMed1995

Tacrolimus: a potential new treatment for autoimmune chronic active hepatitis: results of an open-label preliminary trial.

Autoimmune chronic active hepatitis (CAH-A) is a chronic liver disease of unknown etiology that is believed to have an autoimmune pathogenesis. The disease is slowly progressive until hepatic failure and portal hypertension develop and either death or liver transplantation occur. Currently, the only widely recognized therapy is the administration of glucocorticoids, which have both anti-inflammatory and immunosuppressive actions. Many patients cannot tolerate such therapy because of the psychiatric, osteoporotic, and weight-enhancing actions of steroids. Tacrolimus (FK 506) is a new macrolide antibiotic that has an immunosuppressive activity that is estimated to be 10-200 times greater than that of cyclosporine. Because of its greater immunosuppressive activity, we have used it in the treatment of 21 patients with autoimmune chronic active hepatitis. Before each subject was treated, a liver biopsy and a panel of hematological, serological, and biochemical parameters were assessed. The Tacrolimus was administered orally at 12-h intervals, and the dose was controlled by monitoring plasma FK trough levels. After 3 months of therapy at an oral dose of 3 mg twice a day, having achieved a median blood level of 0.5 ng/ml, the serum ALT level was reduced by 80%, and the AST level was reduced by 70%. Modest change in the white blood cell count and platelet count were noted. The median BUN level increased from a level of 12 to 18 mg/dl, and the serum creatinine increased from 0.9 to 1.3 mg/dl. These preliminary data demonstrate that: 1) Tacrolimus can be used to successfully treat CAH-A; 2) the response of CAH-A to Tacrolimus treatment is rapid and sustained; and 3) a minor increase in the serum BUN and creatinine levels occurs as a consequence of Tacrolimus treatment. It is anticipated that with continued treatment for periods of 1-2 yr, the natural history of CAH-A will be changed such that hepatic failure and the requirement for liver transplantation may be averted.

Adult↗
PubMed1995

Spatial disorientation-implicated accidents in Canadian forces, 1982-92.

In a recent survey of CF18 aircrew human factors, 44% of pilots reported experience with spatial disorientation (SD), of whom 10% had experienced more than 3 episodes. In order to investigate further, we have completed a retrospective study of SD-implicated category A accidents (where an aircraft is destroyed, declared missing, or damaged beyond economic repair) in the Canadian Forces (CF) during 1982-92. An overview of all SD occurrences (including accidents and incidents) across aircraft types is also presented. Information was gathered concerning the genesis and severity of disorientation so that research effort and pilot training could be appropriately implemented. Mishap investigation summaries involving category A accidents where SD was implicated were obtained from the CF Directorate of Flight Safety and reviewed. We also examined in detail the Board of Inquiry Reports of these accidents. The role of disorientation in these accidents was assessed. There were 62 category A accidents between 1982-92 and, in 14, SD had been assigned as a possible cause factor in the accident records. When divided into the categories of Recognized SD (RSD), Unrecognized SD (USD), and Incapacitating SD (ISD), all but two fell into the category of USD (the pilots were unaware of the disorientation). Of the SD accidents, 11 involved a total loss of 24 lives. The majority of the accidents happened during the day, and pilots' cumulative flying experience did not appear to be a significant factor. According to our assessment, there were two episodes of vestibular origin, involving the somatogravic illusion. Three episodes of disorientation occurred over frozen lakes, one over glassy water, and one over ocean.(ABSTRACT TRUNCATED AT 250 WORDS)

Accidents, Aviation↗
PubMed1995

The Oklahoma-Pittsburgh experience with interferon alpha in the treatment of HCV disease.

Interferon alpha (IFN) is the only Food and Drug Administration (FDA)-approved therapy available for the treatment of chronic hepatitis C. The ideal dose and frequency of IFN administration that produces the greatest number of patient responders with the least number of relapses following drug withdrawal remains unclear. METHODS. One hundred seventeen patients recruited over a five-year period with chronic hepatitis C were divided into four groups and treated with progressively larger doses. The rate of clinical responses defined as a loss of detectable hepatitis C virus-ribonucleic acid (HCV-RNA) in serum by polymerase chain reaction (PCR) and normalization of the serum ALT (abnormal alanine aminotransferase) for each group was calculated. RESULTS. As the dose of IFN administration increased, the response rate defined by the absence of HCV-RNA in the patient's serum after six months of follow-up increased from 7.7% to 26.6%. If the end point utilized was HCV-RNA negativity after six months of treatment, the response rate varied from 19.2% to 30%. Using the less difficult end point of a normal ALT level, the response rates varied from 32.1% to 63.3% after six months of therapy and from 10.7% to 26.7% after six months of follow-up. CONCLUSIONS. This experience demonstrates that both the response rate at the end of therapy and after six months of follow-up improves with an increase in dose of IFN administered over a six-month period.

Adult↗